1. Field of the Invention
This invention relates to the field of optical readers, and more particularly to devices adapted to discern the presence or absence of any of a variety of handwritten marks on printed forms bearing print-delineated areas for receiving the marks, such as lottery card entries, multiple choice cards, standardized test forms and the like.
2. Prior Art
Apparatus for analyzing video images of sheet material are known for certain uses. U.S. Pat. No. 4,493,108--Fryer et al teaches an apparatus for analytically dividing a printed or written document into relatively large image fields, whereupon markings in the particular fields can be more carefully analyzed for types of data expected to occur in such fields. Similar devices distinguish currency, marked envelopes, package markings, etc. The most frequent use of such devices is in connection with reading bank codes and amounts printed on checks. U.S. Pat. No. 4,326,258--de la Guardia analyzes a check by defining grey levels for sampled picture elements (pixels) in an image developed in data by moving the check transversely through a linear arry of periodically-sampled optical elements.
Image analysis devices based upon grey level data techniques usually convert the grey level data to a map of black or white pixels based upon some threshold stored for the device or calculated from the data. The black/white pixel pattern is then analyzed for spatial correlation with stored patterns. This is effective in connection with analysis of printed or written characters that correspond closely to expected forms. U.S. Pat. No. 4,490,853--Nally et al teaches a matrix character reading system in which a device developing a matrix of pixel data from a moving check or the like analyzes the patterns of grey levels to define dark and light pixels and to decode numeric characters printed on the check in distinctive magnetic or contrrasting ink shapes. The character fonts for these forms are especially adapted to optimally distinguish between numerals such that errors in decoding the printed numerals are less likely and the process is less sensitive to positioning and timing errors.
U.S. Pat. No. 4,450,579--Nakashima et al concerns a device in which a TV monitor camera is made controllably-rotatable around its viewing axis in order to enable correction of rotational misalignment of parts being viewed. The patent in particular teaches such a device for aligning the image with respect to semiconductor mounting pads that define a known spider shape.
Data is often manually coded on printed forms by users choosing and marking their choices of numerically marked boxes or the like. The boxes may be spaced on the forms or printed to indicate specific numbers or other data choices. The marks may be coarse slashes, lines, x-shapes, dots, rectangles, etc. In the reading of handwritten marks, for example on lottery card entries or standardized tests, it is possible to scan the image of a card or test paper, and to interpret the timing and position of dark marks on the card or sheet as data. This is normally accomplished by moving the card or sheet at a known rate transversely to a linear array of optical sensors. By correlating the timing or linear advance of the card or sheet with the lightness or darkness detected by each individual sensor, data is encoded to reflect spatial positions of pencil marks or the like on the card. This problem has some similarity to reading punched cards, but is complicated because the marks are not as standardized as machine made punch holes in either shape or position.
The designer of a mark reading device is subject to a dilemma. If the reader must be particularly fast or if a card is to encode a substantial quantity of data, it is necessary to position the potential mark choice boxes or the like close together, and to make them rather small. Alternatively, it may be necessary to move the card quickly through the array of sensors. Such efforts to improve processing speed or data density make analysis of the image even more demanding. Furthermore, improvements in the speed and accuracy of detecting data are expensive. These may relate to closer dimensional control of the cards, more powerful light sources to develop better images, more sensitive optical elements and greater precision in card feeding. Each of these changes can be expensive and most demanding in terms of precision, maintenance and the like.
Expensive high performance feeding or reading equipment might be justified in connection with certain applications such as standardized tests, in which a large part of all the marked test forms are to be centrally processed by one or a few processing offices. High performance equipment might also be appropriate for reading currency. On the other hand, it may not be cost justified to provide all point of sale terminals and all terminals for processing lottery card entries and similar hand-marked data cards with such sophistication. These cards and their readers should be dependable but simple and inexpensive. Their readers should be insensitive to variations in the cards and the manner in which marks are placed on the cards, and detection equipment should be accurate and inexpensive. With these objects in mind, it is difficult to justify the analytical sophistication and high precision hardware that might be used for devices that read shaped account numbers from checks, or otherwise perform relatively slow but important and precise analyses.
Lottery card systems have certain objects that do not compare with the objects of systems for encoding data from printed checks or other simple data entry operations. For example, a great deal of the player satisfaction and interest in a lottery game is related to the specific type of game. Games preferably have features that increase excitement of play, such as similarities to real-life chance events. Frequently, games of chance will be directed to sports, having some indicia suggesting baseball, football, horse racing or the like. Lottery cards especially adapted to such games of chance are appealing to consumers. Furthermore, different consumers may have different tastes in the type of game or the related sport or other terms on which they prefer to play.
Inexpensive marked card readers may also be subject to other uses such as fast-service retail establishments where customers make selections by marking cards. In this case, product attributes (e.g., the appearance of appetizing food, etc.) can be printed on the cards to be marked with selections.
A number of conventional features are used in the art to facilitate character location and character recognition by machine. These devices are based upon expecting distinguishable characters (e.g., having a known size and shape) to appear (or not appear) in the image at a predetermined location relative to other features or relative to the borders of the image. It is known, for example, to use spaced identification marks at the borders of the card for triggering imting signals. In such a device for example, detection of a timing mark causes loading of the current light/dark status of each photosensor in a row into a register. Timing marks are not used in the art as a means to discern among a plurality of possible lottery card entries, or to form a basis for mapping of an instantaneously-recorded matrix of data in an image field, to correct for variations in position due to x-y displacement and skew. Such displacement and skew are the frequent result of feeding of cards without a great deal of precision, or feeding cards that do not conform precisely to nominal dimensions due to folding or spindling, or imprecise manufacture, which attributes are only to be expected of lottery player entry cards.
According to the invention, the image of a player entry card with locating marks is recorded instantaneously. A stationary image is developed by stopping the card or strobing a light source illuminating a slowly moving card. Problems with misalignment and skew are minimized because the card image data can be analyzed by its locating marks. Therefore, problems that would otherwise be associated with misalignment of a card transversely fed through a linear array of photosensors do not occur. The video or other image is sampled and encoded for its grey levels at spaced pixels in a matrix covering at least the potential mark area of the card and an area of printed identification marks on the card. The identification marks, which are spaced, define a baseline against which the potential mark areas can be mapped.
Grey level pixel data is analyzed using a comparison especially adapted for use with handwritten marks, said marks being variable in shape and in darkness. The unit compares the darkness of pixels at successive pixels in potential mark areas with the immediately adjacent pixels in a pattern of a star. The pixel in the central part of this comparison zone, or the "target" pixel, is weighted by a factor equal to the number of adjacent points with which the target pixel will be compared. For example, the target pixel value is multiplied by 4, and the summed value of 4 adjacent pixels is subtracted therefrom. The resulting difference exceeds a threshold if there is an edge of contrast anywhere in the star-shaped pattern analyzed. This analysis is preferably done on a number of target pixels within the box, bracket or other printed delineation of a mark-receiving area. A sufficient number of such edges is taken to indicate the presence of a mark.
Inasmuch as the invention detects edges of contrast in the field of analysis, the lightness or darkness of the overall card and the lightness or darkness in the general field of analysis are both irrelevant. Detectable edges are therefore found even in marks on smudged areas characteristic of pencil erasures.
The invention is inexpensive enough for practical use in point of sale devices. It is also quite accurate and is particularly effective with handwritten mark sensing of lottery cards.